Arrastrar y colocar imágenes en java

Question

Lo que quiero es arrastrar y soltar una imagen de JPanel a otra. Pude hacerlo utilizando bibliotecas dnd. Pero estoy atascado porque no puedo arrastrar la imagen desde el panel donde la dejé caer (del destino de caída). eso significa que droptarget también necesita actuar como un dragSource. ¿Cómo hago esto?

Answer 1

Tal vez esto ayuda:

http://www.java2s.com/Code/Java/Swing-JFC/DragPictureDemo2.htm

/* From http://java.sun.com/docs/books/tutorial/index.html */ 

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/* 
* DragPictureDemo2.java is a 1.4 example that requires the following files: 
* Picture.java DTPicture.java PictureTransferHandler.java 
* TransferActionListener.java images/Maya.jpg images/Anya.jpg images/Laine.jpg 
* images/Cosmo.jpg images/Adele.jpg images/Alexi.jpg 
*/ 

import java.awt.BorderLayout; 
import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.Graphics; 
import java.awt.GridLayout; 
import java.awt.Image; 
import java.awt.KeyboardFocusManager; 
import java.awt.datatransfer.DataFlavor; 
import java.awt.datatransfer.Transferable; 
import java.awt.datatransfer.UnsupportedFlavorException; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.awt.event.FocusEvent; 
import java.awt.event.FocusListener; 
import java.awt.event.InputEvent; 
import java.awt.event.KeyEvent; 
import java.awt.event.MouseEvent; 
import java.awt.event.MouseListener; 
import java.awt.event.MouseMotionListener; 
import java.beans.PropertyChangeEvent; 
import java.beans.PropertyChangeListener; 
import java.io.File; 
import java.io.IOException; 
import java.net.MalformedURLException; 

import javax.accessibility.Accessible; 
import javax.swing.Action; 
import javax.swing.ActionMap; 
import javax.swing.BorderFactory; 
import javax.swing.ImageIcon; 
import javax.swing.InputMap; 
import javax.swing.JComponent; 
import javax.swing.JFrame; 
import javax.swing.JMenu; 
import javax.swing.JMenuBar; 
import javax.swing.JMenuItem; 
import javax.swing.JPanel; 
import javax.swing.KeyStroke; 
import javax.swing.TransferHandler; 

//A version of DragPictureDemo that creates an 
//Edit menu with cut/copy/paste actions. 
//This demo adds a class called TransferActionDemo 
//that transfers the cut/copy/paste menu action 
//to the currently focused component. 
public class DragPictureDemo2 extends JPanel { 

    DTPicture pic1, pic2, pic3, pic4, pic5, pic6, pic7, pic8, pic9, pic10, 
     pic11, pic12; 

    static String mayaString = "Maya"; 

    static String anyaString = "Anya"; 

    static String laineString = "Laine"; 

    static String cosmoString = "Cosmo"; 

    static String adeleString = "Adele"; 

    static String alexiString = "Alexi"; 

    PictureTransferHandler picHandler; 

    public DragPictureDemo2() { 
    super(new BorderLayout()); 
    picHandler = new PictureTransferHandler(); 
    //Since we are using keyboard accelerators, we don't 
    //need the component to install its own input map 
    //bindings. 
    DTPicture.setInstallInputMapBindings(false); 

    JPanel mugshots = new JPanel(new GridLayout(4, 3)); 
    pic1 = new DTPicture(createImageIcon("images/" + mayaString + ".jpg", 
     mayaString).getImage()); 
    pic1.setTransferHandler(picHandler); 
    mugshots.add(pic1); 
    pic2 = new DTPicture(createImageIcon("images/" + anyaString + ".jpg", 
     anyaString).getImage()); 
    pic2.setTransferHandler(picHandler); 
    mugshots.add(pic2); 
    pic3 = new DTPicture(createImageIcon("images/" + laineString + ".jpg", 
     laineString).getImage()); 
    pic3.setTransferHandler(picHandler); 
    mugshots.add(pic3); 
    pic4 = new DTPicture(createImageIcon("images/" + cosmoString + ".jpg", 
     cosmoString).getImage()); 
    pic4.setTransferHandler(picHandler); 
    mugshots.add(pic4); 
    pic5 = new DTPicture(createImageIcon("images/" + adeleString + ".jpg", 
     adeleString).getImage()); 
    pic5.setTransferHandler(picHandler); 
    mugshots.add(pic5); 
    pic6 = new DTPicture(createImageIcon("images/" + alexiString + ".jpg", 
     alexiString).getImage()); 
    pic6.setTransferHandler(picHandler); 
    mugshots.add(pic6); 

    //These six components with no pictures provide handy 
    //drop targets. 
    pic7 = new DTPicture(null); 
    pic7.setTransferHandler(picHandler); 
    mugshots.add(pic7); 
    pic8 = new DTPicture(null); 
    pic8.setTransferHandler(picHandler); 
    mugshots.add(pic8); 
    pic9 = new DTPicture(null); 
    pic9.setTransferHandler(picHandler); 
    mugshots.add(pic9); 
    pic10 = new DTPicture(null); 
    pic10.setTransferHandler(picHandler); 
    mugshots.add(pic10); 
    pic11 = new DTPicture(null); 
    pic11.setTransferHandler(picHandler); 
    mugshots.add(pic11); 
    pic12 = new DTPicture(null); 
    pic12.setTransferHandler(picHandler); 
    mugshots.add(pic12); 

    setPreferredSize(new Dimension(450, 630)); 
    add(mugshots, BorderLayout.CENTER); 
    setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20)); 
    } 

    //Create an Edit menu to support cut/copy/paste. 
    public JMenuBar createMenuBar() { 
    JMenuItem menuItem = null; 
    JMenuBar menuBar = new JMenuBar(); 
    JMenu mainMenu = new JMenu("Edit"); 
    mainMenu.setMnemonic(KeyEvent.VK_E); 
    TransferActionListener actionListener = new TransferActionListener(); 

    menuItem = new JMenuItem("Cut"); 
    menuItem.setActionCommand((String) TransferHandler.getCutAction() 
     .getValue(Action.NAME)); 
    menuItem.addActionListener(actionListener); 
    menuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X, 
     ActionEvent.CTRL_MASK)); 
    menuItem.setMnemonic(KeyEvent.VK_T); 
    mainMenu.add(menuItem); 
    menuItem = new JMenuItem("Copy"); 
    menuItem.setActionCommand((String) TransferHandler.getCopyAction() 
     .getValue(Action.NAME)); 
    menuItem.addActionListener(actionListener); 
    menuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_C, 
     ActionEvent.CTRL_MASK)); 
    menuItem.setMnemonic(KeyEvent.VK_C); 
    mainMenu.add(menuItem); 
    menuItem = new JMenuItem("Paste"); 
    menuItem.setActionCommand((String) TransferHandler.getPasteAction() 
     .getValue(Action.NAME)); 
    menuItem.addActionListener(actionListener); 
    menuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_V, 
     ActionEvent.CTRL_MASK)); 
    menuItem.setMnemonic(KeyEvent.VK_P); 
    mainMenu.add(menuItem); 

    menuBar.add(mainMenu); 
    return menuBar; 
    } 

    /** Returns an ImageIcon, or null if the path was invalid. */ 
    protected static ImageIcon createImageIcon(String path, String description) { 
     try { 
      File imageURL = new File(path); 

      if (imageURL == null) { 
       System.err.println("Resource not found: " + path); 
       return null; 
      } else { 
     return new ImageIcon(imageURL.toURI().toURL(), description); 
      } 
    } catch(MalformedURLException e) { 
     e.printStackTrace(); 
    } 
    return null; 
    } 

    /** 
    * Create the GUI and show it. For thread safety, this method should be 
    * invoked from the event-dispatching thread. 
    */ 
    private static void createAndShowGUI() { 
    //Make sure we have nice window decorations. 
    JFrame.setDefaultLookAndFeelDecorated(true); 

    //Create and set up the window. 
    JFrame frame = new JFrame("DragPictureDemo2"); 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

    //Create and set up the menu bar and content pane. 
    DragPictureDemo2 demo = new DragPictureDemo2(); 
    frame.setJMenuBar(demo.createMenuBar()); 
    demo.setOpaque(true); //content panes must be opaque 
    frame.setContentPane(demo); 

    //Display the window. 
    frame.pack(); 
    frame.setVisible(true); 
    } 

    public static void main(String[] args) { 
    //Schedule a job for the event-dispatching thread: 
    //creating and showing this application's GUI. 
    javax.swing.SwingUtilities.invokeLater(new Runnable() { 
     public void run() { 
     createAndShowGUI(); 
     } 
    }); 
    } 
} 

/* 
* DTPicture.java is used by the 1.4 DragPictureDemo.java example. 
*/ 

//A subclass of Picture that supports Data Transfer. 

class DTPicture extends Picture implements MouseMotionListener { 
    private MouseEvent firstMouseEvent = null; 

    private static boolean installInputMapBindings = true; 

    public DTPicture(Image image) { 
    super(image); 
    addMouseMotionListener(this); 

    //Add the cut/copy/paste key bindings to the input map. 
    //Note that this step is redundant if you are installing 
    //menu accelerators that cause these actions to be invoked. 
    //DragPictureDemo does not use menu accelerators and, since 
    //the default value of installInputMapBindings is true, 
    //the bindings are installed. DragPictureDemo2 does use 
    //menu accelerators and so calls setInstallInputMapBindings 
    //with a value of false. Your program would do one or the 
    //other, but not both. 
    if (installInputMapBindings) { 
     InputMap imap = this.getInputMap(); 
     imap.put(KeyStroke.getKeyStroke("ctrl X"), TransferHandler 
      .getCutAction().getValue(Action.NAME)); 
     imap.put(KeyStroke.getKeyStroke("ctrl C"), TransferHandler 
      .getCopyAction().getValue(Action.NAME)); 
     imap.put(KeyStroke.getKeyStroke("ctrl V"), TransferHandler 
      .getPasteAction().getValue(Action.NAME)); 
    } 

    //Add the cut/copy/paste actions to the action map. 
    //This step is necessary because the menu's action listener 
    //looks for these actions to fire. 
    ActionMap map = this.getActionMap(); 
    map.put(TransferHandler.getCutAction().getValue(Action.NAME), 
     TransferHandler.getCutAction()); 
    map.put(TransferHandler.getCopyAction().getValue(Action.NAME), 
     TransferHandler.getCopyAction()); 
    map.put(TransferHandler.getPasteAction().getValue(Action.NAME), 
     TransferHandler.getPasteAction()); 
    } 

    public void setImage(Image image) { 
    this.image = image; 
    this.repaint(); 
    } 

    public void mousePressed(MouseEvent e) { 
    //Don't bother to drag if there is no image. 
    if (image == null) 
     return; 

    firstMouseEvent = e; 
    e.consume(); 
    } 

    public void mouseDragged(MouseEvent e) { 
    //Don't bother to drag if the component displays no image. 
    if (image == null) 
     return; 

    if (firstMouseEvent != null) { 
     e.consume(); 

     //If they are holding down the control key, COPY rather than MOVE 
     int ctrlMask = InputEvent.CTRL_DOWN_MASK; 
     int action = ((e.getModifiersEx() & ctrlMask) == ctrlMask) ? TransferHandler.COPY 
      : TransferHandler.MOVE; 

     int dx = Math.abs(e.getX() - firstMouseEvent.getX()); 
     int dy = Math.abs(e.getY() - firstMouseEvent.getY()); 
     //Arbitrarily define a 5-pixel shift as the 
     //official beginning of a drag. 
     if (dx > 5 || dy > 5) { 
     //This is a drag, not a click. 
     JComponent c = (JComponent) e.getSource(); 
     TransferHandler handler = c.getTransferHandler(); 
     //Tell the transfer handler to initiate the drag. 
     handler.exportAsDrag(c, firstMouseEvent, action); 
     firstMouseEvent = null; 
     } 
    } 
    } 

    public void mouseReleased(MouseEvent e) { 
    firstMouseEvent = null; 
    } 

    public void mouseMoved(MouseEvent e) { 
    } 

    //This method is necessary because DragPictureDemo and 
    //DragPictureDemo2 both use this class and DragPictureDemo 
    //needs to have the input map bindings installed for 
    //cut/copy/paste. DragPictureDemo2 uses menu accelerators 
    //and does not need to have the input map bindings installed. 
    //Your program would use one approach or the other, but not 
    //both. The default for installInputMapBindings is true. 
    public static void setInstallInputMapBindings(boolean flag) { 
    installInputMapBindings = flag; 
    } 

    public static boolean getInstallInputMapBindingds() { //for completeness 
    return installInputMapBindings; 
    } 
} 

/* 
* Picture.java is used by the 1.4 TrackFocusDemo.java and DragPictureDemo.java 
* examples. 
*/ 

class Picture extends JComponent implements MouseListener, FocusListener, 
    Accessible { 
    Image image; 

    public Picture(Image image) { 

    this.image = image; 
    setFocusable(true); 
    addMouseListener(this); 
    addFocusListener(this); 
    } 

    public void mouseClicked(MouseEvent e) { 
    //Since the user clicked on us, let's get focus! 
    requestFocusInWindow(); 
    } 

    public void mouseEntered(MouseEvent e) { 
    } 

    public void mouseExited(MouseEvent e) { 
    } 

    public void mousePressed(MouseEvent e) { 
    } 

    public void mouseReleased(MouseEvent e) { 
    } 

    public void focusGained(FocusEvent e) { 
    //Draw the component with a red border 
    //indicating that it has focus. 
    this.repaint(); 
    } 

    public void focusLost(FocusEvent e) { 
    //Draw the component with a black border 
    //indicating that it doesn't have focus. 
    this.repaint(); 
    } 

    protected void paintComponent(Graphics graphics) { 
    Graphics g = graphics.create(); 

    //Draw in our entire space, even if isOpaque is false. 
    g.setColor(Color.WHITE); 
    g.fillRect(0, 0, image == null ? 125 : image.getWidth(this), 
     image == null ? 125 : image.getHeight(this)); 

    if (image != null) { 
     //Draw image at its natural size of 125x125. 
     g.drawImage(image, 0, 0, this); 
    } 

    //Add a border, red if picture currently has focus 
    if (isFocusOwner()) { 
     g.setColor(Color.RED); 
    } else { 
     g.setColor(Color.BLACK); 
    } 
    g.drawRect(0, 0, image == null ? 125 : image.getWidth(this), 
     image == null ? 125 : image.getHeight(this)); 
    g.dispose(); 
    } 
} 

/* 
* PictureTransferHandler.java is used by the 1.4 DragPictureDemo.java example. 
*/ 

class PictureTransferHandler extends TransferHandler { 
    DataFlavor pictureFlavor = DataFlavor.imageFlavor; 

    DTPicture sourcePic; 

    boolean shouldRemove; 

    public boolean importData(JComponent c, Transferable t) { 
    Image image; 
    if (canImport(c, t.getTransferDataFlavors())) { 
     DTPicture pic = (DTPicture) c; 
     //Don't drop on myself. 
     if (sourcePic == pic) { 
     shouldRemove = false; 
     return true; 
     } 
     try { 
     image = (Image) t.getTransferData(pictureFlavor); 
     //Set the component to the new picture. 
     pic.setImage(image); 
     return true; 
     } catch (UnsupportedFlavorException ufe) { 
     System.out.println("importData: unsupported data flavor"); 
     } catch (IOException ioe) { 
     System.out.println("importData: I/O exception"); 
     } 
    } 
    return false; 
    } 

    protected Transferable createTransferable(JComponent c) { 
    sourcePic = (DTPicture) c; 
    shouldRemove = true; 
    return new PictureTransferable(sourcePic); 
    } 

    public int getSourceActions(JComponent c) { 
    return COPY_OR_MOVE; 
    } 

    protected void exportDone(JComponent c, Transferable data, int action) { 
    if (shouldRemove && (action == MOVE)) { 
     sourcePic.setImage(null); 
    } 
    sourcePic = null; 
    } 

    public boolean canImport(JComponent c, DataFlavor[] flavors) { 
    for (int i = 0; i < flavors.length; i++) { 
     if (pictureFlavor.equals(flavors[i])) { 
     return true; 
     } 
    } 
    return false; 
    } 

    class PictureTransferable implements Transferable { 
    private Image image; 

    PictureTransferable(DTPicture pic) { 
     image = pic.image; 
    } 

    public Object getTransferData(DataFlavor flavor) 
     throws UnsupportedFlavorException { 
     if (!isDataFlavorSupported(flavor)) { 
     throw new UnsupportedFlavorException(flavor); 
     } 
     return image; 
    } 

    public DataFlavor[] getTransferDataFlavors() { 
     return new DataFlavor[] { pictureFlavor }; 
    } 

    public boolean isDataFlavorSupported(DataFlavor flavor) { 
     return pictureFlavor.equals(flavor); 
    } 
    } 
} 

/* 
* TransferActionListener.java is used by the 1.4 DragPictureDemo.java example. 
*/ 

/* 
* A class that tracks the focused component. This is necessary to delegate the 
* menu cut/copy/paste commands to the right component. An instance of this 
* class is listening and when the user fires one of these commands, it calls 
* the appropriate action on the currently focused component. 
*/ 

class TransferActionListener implements ActionListener, PropertyChangeListener { 
    private JComponent focusOwner = null; 

    public TransferActionListener() { 
    KeyboardFocusManager manager = KeyboardFocusManager 
     .getCurrentKeyboardFocusManager(); 
    manager.addPropertyChangeListener("permanentFocusOwner", this); 
    } 

    public void propertyChange(PropertyChangeEvent e) { 
    Object o = e.getNewValue(); 
    if (o instanceof JComponent) { 
     focusOwner = (JComponent) o; 
    } else { 
     focusOwner = null; 
    } 
    } 

    public void actionPerformed(ActionEvent e) { 
    if (focusOwner == null) 
     return; 
    String action = (String) e.getActionCommand(); 
    Action a = focusOwner.getActionMap().get(action); 
    if (a != null) { 
     a.actionPerformed(new ActionEvent(focusOwner, 
      ActionEvent.ACTION_PERFORMED, null)); 
    } 
    } 
}